Injection molding flow control apparatus and method

ABSTRACT

In an injection molding machine having upstream and downstream channels communicating with each other for delivering fluid material to one or more mold cavities, apparatus for controlling delivery of the melt material from the channels to the one or more mold cavities, each channel having an axis, the downstream channel having an axis intersecting a gate of a cavity of a mold, the upstream channel having an axis not intersecting the gate and being associated with an upstream actuator interconnected to an upstream melt flow controller disposed at a selected location within the upstream channel, the apparatus comprising a sensor for sensing a selected condition of the melt material at a position downstream of the upstream melt flow controller; an actuator controller interconnected to the upstream actuator, the actuator controller comprising a computer interconnected to a sensor for receiving a signal representative of the selected condition sensed by the sensor, the computer including an algorithm utilizing a value indicative of the signal received from the sensor as a variable for controlling operation of the upstream actuator; wherein the upstream melt flow controller is adapted to control the rate of flow of the fluid material at the selected location within the upstream channel according to the algorithm.

RELATED APPLICATIONS

This application claims the benefit of priority under 35 USC Section 119to U.S. provisional patent application Ser. No. 60/431,923 filed Dec. 9,2002, the disclosure of which is incorporated herein by reference in itsentirety as if fully set forth herein.

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/269,927 filed Oct. 11, 2002 which is a continuation of U.S.application Ser. No. 09/400,533 issued as U.S. Pat. No. 6,464,909 onOct. 15, 2002.

The disclosures of all of the following are incorporated by reference intheir entirety as if fully set forth herein: U.S. Pat. No. 5,894,025,U.S. Pat. No. 6,062,840, U.S. Pat. No. 6,294,122, U.S. Pat. No.6,309,208, U.S. Pat. No. 6,287,107, U.S. Pat. No. 6,343,921, U.S. Pat.No. 6,343,922, U.S. Pat. No. 6,254,377, U.S. Pat. No. 6,261,075, U.S.Pat. No. 6,361,300, U.S. Pat. No. 6,464,909, U.S. patent applicationSer. No. 10/214,118, filed Aug. 8, 2002 (7006), U.S. patent applicationSer. No. 09/699,856 filed Oct. 30, 2000 (7056), U.S. patent applicationSer. No. 10/269,927 filed Oct. 11, 2002 (7031), U.S. application Ser.No. 09/503,832 filed Feb. 15, 2000 (7053), U.S. application Ser. No.09/656,846 filed Sep. 7, 2000 (7060), U.S. application Ser. No.10/006,504 filed Dec. 3, 2001, (7068) and U.S. application Ser. No.10/101,278 filed Mar. 19, 2002 (7070).

BACKGROUND OF THE INVENTION

Injection molding systems have been developed having flow controlmechanisms that move at high speed over relatively short periods of timeto control the rate of flow of fluid material that is being injected toa mold cavity. The range of distance of movement or travel of the flowcontrol mechanisms is also relatively small. Computer/algorithmelectronic controls have been developed to effect such movements on thebasis of a variable input that corresponds to a sensed condition of thefluid material being injected or another sensed property, state orcondition of a component of the apparatus or the energy, pressure orpower used to operate an operating mechanism associated with theapparatus that is used to control the flow velocity of the fluidmaterial.

The accuracy and precision of such algorithmically controlled movementdepends on the accuracy/precision of the sensed condition as a measureof flow velocity at any given point in time or at any given locationwithin the fluid flow stream where the fluid or machine property isbeing sensed by a sensor.

SUMMARY OF THE INVENTION

In accordance with the invention there is provided an injection moldingapparatus comprising: a manifold having a channel for delivering a flowof a fluid material to a gate of a mold cavity during an injectioncycle; a fluid flow controller adapted to move within the channel alonga path of travel; a position sensor for detecting one or more positionsof the fluid flow controller along the path of travel; a mastercontroller interconnected to the fluid flow controller for controllingmovement of the fluid flow controller along the path of travel, themaster controller including an algorithm having a set of instructionsthat limit the extent of travel of the fluid flow controller along thepath of travel during the injection cycle to one or more preselectedpositions, the one or more preselected positions being detected by theposition sensor, the position sensor sending a signal indicative ofdetection of the one or more preselected positions of travel to themaster controller during the injection cycle, the master controllerlimiting travel of the fluid flow controller beyond the one or morepreselected positions upon receipt of the signal.

The one or more preselected positions typically comprise one or morepositions at which the fluid flow controller allows flow of the fluidmaterial through the channel at a maximum rate of flow.

The algorithm can include a set of instructions that control movement ofthe fluid flow controller beyond the one or more preselected positionsupon occurrence of a predetermined event during the injection cycle. Thepredetermined event typically comprises one or more of (a) an expirationof a predetermined amount of time from a selected point in time duringan injection cycle, (b) detection of a selected degree of a condition ofthe fluid material or (c) detection of a selected degree of a selectedproperty, position or operating condition of an operating component ofthe hotrunner/manifold apparatus or the injection molding machine.

The fluid flow controller is preferably movable along the path of travelbetween a range of variable flow rate positions, a range of maximum flowpositions and one or more closed flow positions, wherein the one or morepreselected positions to which travel of the flow controller is limitedduring the injection cycle comprise one or more of the maximum flowpositions.

The apparatus preferably further comprises a material condition sensorthat senses a selected condition of the fluid material, the algorithmutilizing a value indicative of the sensed condition as a variable tocontrol movement of the fluid flow controller to one or more variableflow rate positions along the path of travel. The material conditionsensor typically comprises a pressure sensor.

The fluid flow controller typically comprises a valve pin having a firstend interconnected to an actuator and a control surface distal of thefirst end that is movable to a plurality of varying flow rate positions,the actuator being interconnected to the algorithm, the algorithmincluding a set of instructions for controlling movement of the controlsurface to the one or more varying flow rate positions during theinjection cycle.

The valve pin can have a second end that closes the gate in a forwardclosed position, the control surface being intermediate the first andsecond ends and controllably movable to the plurality of varying flowrate positions. The valve pin is preferably movable between theplurality of varying flow rate positions, a range of maximum flowpositions and the forward closed position, wherein the one or morepreselected positions to which travel of the flow controller is limitedduring the injection cycle comprise one or more of the maximum flowpositions.

Upstream movement of the valve pin to successive ones of the pluralityof varying flow rate positions typically decreases the rate of flow offluid material.

In another aspect of the invention there is provided an injectionmolding apparatus comprising a manifold having a channel for deliveringa flow of a fluid material to a gate of a mold cavity during aninjection cycle; a valve pin adapted to reciprocate through the channelalong a path of travel; a condition sensor for detecting a selectedcondition of the fluid material; a position sensor for detecting one ormore positions of the valve pin along the path of travel; a controllerinterconnected to the valve pin for controlling movement of the valvepin along the path of travel, the controller including an algorithmhaving a set of instructions that control movement of the valve pin to aplurality of varying flow rate positions along the path of travel basedon values determined by the selected condition of the fluid materialsensed by the condition sensor during the injection cycle; the algorithmincluding a set of instructions that limit the extent of upstream ordownstream travel of the pin along the path of travel during theinjection cycle to one or more preselected positions, the one or morepreselected positions being detected by the position sensor, theposition sensor sending a signal indicative of detection of the one ormore preselected positions of travel to the controller during theinjection cycle.

In another aspect of the invention there is provided an injectionmolding apparatus comprising a manifold having a channel for deliveringa flow of a selected fluid material to a gate of a mold; a valve pinadapted to reciprocate through the channel, the valve pin having a firstend coupled to an actuator, a second end that closes the gate in aforward closed position, and a control surface intermediate said firstand second ends for adjusting the rate of material flow during aninjection cycle, wherein the actuator is interconnected to a controllerhaving a program for controlling reciprocation of the valve pinaccording to a predetermined algorithm; a condition sensor for detectinga selected condition of the fluid material, the algorithm utilizing avalue determined by the selected condition detected by the conditionsensor to control reciprocation of the valve pin; a position sensor thatsenses position of the valve pin, the algorithm utilizing a valuedetermined by one or more sensed positions of the valve pin to limitmovement of the valve pin during the injection cycle beyond the one ormore sensed positions during the injection cycle.

The invention also provides a valve assembly for controlling fluid flowrate in an injection molding apparatus, wherein the assembly comprises:

an actuator comprising a housing and a driven piston slidably disposedwithin the housing for reciprocal movement within the housing to one ormore fluid flow rate control positions, the actuator beinginterconnected to a fluid flow controller and a master controller havingan algorithm that includes a set of instructions for controllingmovement of the piston;

a position sensor adapted to sense movement of the piston or the fluidflow controller, the position sensor being interconnected to the mastercontroller for sending signals indicative of the position of the pistonto the master controller, the algorithm utilizing values correspondingto the signals sent by the position sensor.

The invention further provides a method for controlling injection of afluid through a gate of a mold cavity in an injection molding apparatus,the injection molding apparatus comprising a manifold having a channelfor delivering a flow of the fluid material to the gate of the moldcavity during an injection cycle and a fluid flow controller adapted tobe moved by an actuator to a plurality of positions along a path oftravel within the channel, the method comprising:

predetermining one or more positions along the path of travel during aninjection cycle that generate a rate of flow of the fluid material bythe fluid flow controller that fills the mold cavity with the fluidmaterial according to a predetermined profile of one or more positions;

injecting the fluid through the channel;

sensing the one or more positions of the fluid flow controller along thepath of travel;

sending signals corresponding to the sensed one or more positions to acontroller for controlling movement of the fluid flow controller to thepredetermined one or more positions along the path of travel accordingto an algorithm;

inputting values corresponding to the sent signals to the algorithm, thealgorithm having a set of instructions that compare the input values toa stored set of values corresponding to the predetermined one or morepositions and a set of instructions that instruct the actuator to movethe fluid flow controller to the predetermined one or more positionsduring the injection cycle.

There is also provided a method for controlling injection of a fluidthrough a gate of a mold cavity in an injection molding apparatus, theinjection molding apparatus comprising a manifold having a channel fordelivering a flow of the fluid material to the gate of the mold cavityduring an injection cycle and a fluid flow controller adapted to bemoved by an actuator to a plurality of positions having a pressure ateach position along a path of travel within the channel, the methodcomprising:

predetermining one or more pressures of the fluid material correspondingto a respective one or more positions of the fluid flow controller alongthe path of travel that generate a rate of flow of the fluid material bythe fluid flow controller that fills the mold cavity with the fluidmaterial at a predetermined rate of fill during the injection cycle;

injecting the fluid through the channel under pressure during aninjection cycle;

sensing the pressure of the injected fluid during the injection cycle;

sending signals corresponding to the sensed pressure to a controller forcontrolling movement of the fluid flow controller according to analgorithm;

predetermining a limit position for the fluid flow controller;

sensing the position of the fluid flow controller during the injectioncycle;

sending signals corresponding to the sensed position to the controller;

inputting values corresponding to the sent pressure and position signalsto the algorithm, the algorithm having a set of instructions thatcompare the input pressure values to a stored set of valuescorresponding to the predetermined one or more pressures and a set ofinstructions that compare the input position values to a valuecorresponding to the predetermined limit position;

the algorithm including a set of instructions that instruct the actuatorto move the fluid flow controller to the predetermined one or moreposition corresponding to the predetermined one or more pressures duringthe injection cycle;

the algorithm further including a set of instructions that instruct theactuator to limit movement of the fluid flow controller to the limitposition during selected periods of time during the injection cycle.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and further advantages of the invention may be betterunderstood by referring to the following description in conjunction withthe accompanying drawings in which:

FIG. 1 is a schematic cross-sectional view of one embodiment of aninjection molding system according to the present invention;

FIG. 2 is an isometric exploded view of an actuator usable in the FIG. 1embodiment showing a linear position sensor mountable to an outsidesurface of the actuator housing for use in sensing the position of theactuator cylinder and its associated valve pin along its path of travelwithin the bore/channel of a nozzle leading to the gate of the moldcavity of the FIG. 1 embodiment;

FIG. 3 is a partially schematic, side cross-sectional view of theposition sensor mounting arrangement shown in FIG. 2;

FIGS. 4-6 are side cross-sectional views of an actuator/pin/nozzleassembly as shown in FIG. 1 showing a linear position sensor mountedthereon as shown in FIGS. 2, 3, the valve pin being shown in threeoperating positions during the course of an injection cycle, the startclosed position shown in FIG. 4, an intermediate flow enabled positionshown in FIG. 5 and a maximum flow position shown in FIG. 6;

FIG. 4 a is a side cross-sectional view of another embodiment of theinvention showing an actuator/pin/nozzle assembly as shown in FIG. 1having a switch that detects the position of the piston of the actuatorthrough a window by electromagnetic or magnetic means;

FIG. 4 b is a side cross-sectional view of another embodiment of theinvention showing an actuator/pin/nozzle assembly as shown in FIG. 1having a switch that detects the position of the piston of the actuatorby mechanical contact means;

FIG. 7 is a partially schematic, side cross-section view of anactuator/pin assembly as shown in FIG. 1 with an alternative type ofinductive position sensor mounted at a rear end of the actuator forsensing/recording the position of travel of the cylinder and itsassociated valve pin;

FIG. 8 is a flow chart showing an algorithm that can be used in themaster controller of the FIG. 1 system for controlling movement of theactuator and valve pin during an injection cycle, the algorithm using ascontrol variables signals that are indicative of both the position ofthe cylinder/pin and a selected property (such as pressure) of the fluidbeing routed through a flow channel of the manifold;

FIGS. 9 a-d shows a series of examples of graphs representing actualpressure versus target pressures measured in four injection nozzleshaving position and pressure sensors coupled to a manifold as shown inFIG. 1;

FIGS. 10, 11 are screen icons displayed on interface 114 of FIGS. 5-7which are used to display, create, edit, and store target profiles.

FIG. 12 is a fragmentary cross sectional view of an alternativeembodiment of an injection molding system having flow control thatincludes a valve pin that extends to the gate;

FIG. 13 is an enlarged fragmentary cross-sectional detail of the flowcontrol area;

FIG. 14 is a cross-sectional partially schematic view of anotheralternative embodiment of an injection molding system having flowcontrol in which a load cell behind the valve pin is used to control theflow rate in each injection nozzle;

FIG. 15 is a enlarged fragmentary cross-sectional view of the valve pinand actuator of FIG. 14;

FIG. 16 is an enlarged view of the load cell and valve pin of FIG. 14;

FIGS. 17A and 17B show an enlarged view of the tip of the valve pinclosing the gate and controlling the flow rate, respectively;

FIGS. 18A and 18B shown an alternative structure of an injection moldingnozzle for use in the system shown in FIG. 14;

FIG. 19 is a cross-sectional partially schematic view of an alternativeembodiment of an injection molding system in which a pressure transduceris used to sense the hydraulic pressure supplied to the actuator;

FIG. 20 shows a fragmentary cross-sectional view of an alternativeembodiment of an injection molding system having flow control similar toFIG. 14 in which the pressure transducer is mounted in the mold cavity;and

FIG. 21 is a fragmentary cross-sectional view of an alternativeembodiment of an injection molding system having flow control in whichflow control is effected by measuring the differential pressure of theactuator chambers.

DETAILED DESCRIPTION

FIG. 1 shows one embodiment of an injection molding system 1 accordingto the present invention having a pair of valve gated nozzles 215delivering fluid material to gates 211, which in turn communicate withand deliver fluid material to mold cavity 170. Fluid material isinjected initially under pressure from injection molding machine barrel13 into a main injection channel 17 formed in heated manifold 231 andtravels from channel 17 to the bores or channels 208, 213 of nozzles215. As shown in FIGS. 1, 4-6 an embodiment using an extended pin 200 isdisposed within channels 208, 213 for slidable reciprocating movementalong the axes of channels 208, 213. Channel 17 mates/communicates withbores 208, 213 at an elbow at which a throat or restricted channelsection is disposed where a gap 207 can be formed for controllingmaterial flow rate upstream or away from the gate as described below.

In the FIG. 1 embodiment, a master controller 10 typically comprising adata processor and memory components for processing and storing digitaldata controls the movement of actuators 226 which in turn control thereciprocal movement of pins 200. In the FIG. 1 embodiment, the mastercontroller 10 receives signals from both position sensors and materialcondition sensors. A generic position sensor is designated as item 1000in FIG. 1. Position sensor 1000 can comprise a variety of types ofposition sensing mechanisms as described below. Although shown mountedon the side of the housing 225 of actuators 226 in FIG. 1, depending onthe precise type of position sensor and the precise type of actuator orother mechanical component of the apparatus whose position is to bemeasured, position sensor 1000 is mounted in a location that is mostappropriate to sensing the position of the mechanical component to bemonitored.

As shown in FIG. 1 the master controller 10 sends control signals toservo-valves 212 which control the input and outflow of hydraulic orpneumatic fluid to the sealed chambers of actuators 226. The actuators226 may comprise electrically driven actuators as described for examplein U.S. Pat. No. 6,294,122 the disclosure of which is incorporated byreference in its entirety as if fully set forth herein. Servo-controlmechanisms can be interconnected between the master controller 10 and anelectric actuator, the servomechanism receiving the digital signaloutput of controller 10 for precisely controlling the drive and movementof the shaft of the electric actuator in the same functional manner asthe fluid driven actuators 26 are described herein. Shooting pot rams orcylinders as described in U.S. Pat. Nos. 6,464,909 and 6,287,107 canalso be used in place of valves and valve pins for controlling fluidflow according to the invention. In each case where a particularactuator and its associated servomechanism is used, whether a valve pin,rotary valve or shooting pot ram/cylinder controlled by a hydraulically,pneumatically or electrically driven mechanism, a position sensingmechanism can be used to sense the travel or position of the pin, rotaryvalve or ram/cylinder and send a position indicative signal to themaster controller 10 that includes an algorithm having instructions thatuse a value corresponding to the position indicative signal to controlmovement of the valve pin, rotary valve or ram/cylinder in a manner asdisclosed and claimed herein.

Although only two nozzles and gates are shown in FIG. 1, the inventioncontemplates embodiments that simultaneously control the material flowthrough a plurality of more than two nozzles to a plurality of gates. Inthe embodiment shown, the injection molding system 1 is a single cavity170 system. The present invention can be adapted to any of a variety ofsystems where several nozzle bores or downstream channels 183, 185 feedtwo or more cavities of the same size/configuration or separate cavitiesof different size/configuration or where several bores or channels feeda single non-uniform cavity at different locations/points of entry wherethe volumes to be filled at entry are different as described in, forexample, U.S. patent application Ser. No. 10/328,457 filed Dec. 23,2002, the disclosure of which is incorporated herein by reference in itsentirety as if fully set forth.

A system according to the invention injects plastic material which isheated/melted to a fluid form and injected through the heated manifold231 which maintains the plastic material in fluid form. The invention isalso applicable to other types of injection systems in which it isuseful to control the rate at which another fluid material, e.g.,metallic or composite materials is delivered to a cavity of a mold.

The rate at which fluid material is delivered through the channels 13,17, 208, 213 of the FIG. 1 embodiment is controllably varied by theenlarged bulbous protrusion formed along the length of the valve pin200. As shown in FIGS. 1, 4-6 the valve pin 200 is interconnected at aproximal end to the sliding piston 223 mounted in cylinder housings 225of actuators 226 which in turn are interconnected to servo-controllers212 which are in turn interconnected to master controller 10. As shownin the FIGS. 4-6 embodiment, the master computer or controller 10receives signal inputs indicative of a position of the valve pins 200and their associated pistons 223 from position sensors 100. The positionsensors 100 are mountable on the actuators 226 of FIG. 1 as shown inFIGS. 2, 3 within a slot 103 that can be provided on the side or outersurface of cylinder housing 225 that is lateral to the axis of movementof the piston 223. The position sensors 105 sense the position of travelor stroke 112 of the pins 200 via a sliding rod 102 interconnected toplate 104 which is attached to a distal end of piston 223 as shown inFIGS. 2, 4-6. The sliding rod 102 is spring loaded to maintain contactwith the plate at one end and is interconnected to a potentiometerprovided within sensor 105 at another end. The potentiometer 105 isinterconnected via wiring 105 to controller 10 and sends a voltagesignal that varies with the position of the sliding rod 102 whichfollows and is indicative of the position of travel or stroke 112 of thepin 200 and the piston 223 to which the pin 200 is connected. Thecontroller 10 receives the variable voltage signal and converts thesignal to a value indicative of piston 223 and pin 200 position that isprocessable by the algorithm. The controller 10 includes an algorithmwhich uses as a variable, a value indicative of the position signalreceived from sensor 105 to control the movement of the position of thepins 200 during an injection cycle according to a target profile of pinpositions that has been predetermined in advance for the entireinjection cycle as described more fully below.

Other valve and pin embodiments are usable in the invention. Aparticularly suitable valve and pin design is described in U.S. patentapplication publication no. 2002/0086086, published Jul. 4, 2002, thedisclosure of which is incorporated herein by reference in its entiretyas if fully set forth herein. The pin and valve design of thisapplication show a pin having extended curvilinear bulb upstream of thedistal end of the pin. The bulb controls flow rate upstream and awayfrom the gate while the distal end of the pin closes the gate in amanner analogous to the FIGS. 1, 4-6 valve and pin embodiment describedherein. FIGS. 32-34A of publication no. 2002/0086086 illustrate flowstopped, flow enabled/controlled and gate closed positions analogous tothe positions and configuration depicted in FIGS. 1, 4-6 herein.

Position sensors used in conjunction with the invention typicallycomprise a mechanism that generates a signal that varies according tothe length, degree or amount of travel position of the piston or flowcontroller to which the sensor is connected or interacting with. Suchcontinuously varying output sensors typically generate an output thatvaries in degree of signal strength such as voltage, amperage or thelike. The sensors described with reference to FIGS. 4, 4 a, 7 arecontinuously varying signal sensors. Alternatively, as described withreference to the FIG. 4 b embodiment, a sensor mechanism having a switchthat generates/provides an on or off signal (e.g. a toggle switch) canbe used in other embodiments of the invention where a sensor signal thatcontinuously varies in degree/strength is not feasible for use inconnection with a particular hotrunner/actuator arrangement.

FIG. 4 a shows an alternative position sensing embodiment wherein amagnetic or electromagnetic field is activated or sensed by sensor 130depending on the position of the piston 223 relative to the position ofmounting of the position sensor 130. As shown in FIG. 4 a, a window 132is provided in the upper portion of the piston housing which allows themagnetic or electromagnetic field sensitive switch 130, shown mounted onthe housing 225, to sense the presence of the metal piston 223 throughthe window 132 when the piston 223 is in a position relative to thewindow 132 that is close enough to switch 130 to magnetically orelectromagnetically activate switch 130. When the piston 223 travels toa position that is sufficiently clear of window 132, e.g to a positionas shown in FIG. 5, the switch 130 stops signaling or changes its signalcondition/content to controller 10 thus indicating that the piston 223(and its associated pin 200) has traveled beyond a certain predeterminedlimit position. FIG. 4 b shows another position sensor embodiment wherethe switch 130 comprises a mechanical, contact or interference switch130 a having a mechanical contact member 133 that protrudes radially aslight distance through window 132. Member 133 contacts piston 223 andswitch 130 a is activated when an upper edge 223 a or outer surface 223b of piston 223 travels to a point that is longitudinally aligned withmember 223 such that mechanical contact is made with member 133.

In the FIGS. 4 a, 4 b embodiments, the switch 130, 130 a and the window132 are arranged relative to each other such that switch 130 ceasessensing piston 223 or switch 130 a loses contact with piston 223 whenthe piston 223 and pin 200 have traveled to a “limit position,” i.e. alongitudinal position along the path of travel of the piston where aportion of the piston 223 is not aligned with window 132. When theswitch 130, 130 a ceases sensing or making contact with the piston 223,the controller 10 receives a signal from switch 130, 130 a indicatingthat the switch is deactivated or otherwise different from whateversignal, if any, that the controller was previously receiving from switch130, 130 a when the switch was sensing or in contact with piston 223.Thus the controller 10 receives a signal indicative of the movement ofthe pin 200 or piston 223 to a position at or beyond the predeterminedlimit position. The limit position can be predetermined to be anyselected position of the pin or piston occurring within the timeinterval of an injection cycle. In one embodiment, the limit position ofthe pin/piston is selected to be a position as shown in FIG. 5 where thepin is enabling fluid to flow at a maximum rate and/or the fluid is at amaximum pressure within the time interval of an injection cycle. Asdescribed below with reference to the FIGS. 1, 4-6 embodiments when thecontroller 10 receives a signal that the pin/piston has traveled to orbeyond a selected limit position such as a maximum flow position, thealgorithm includes instructions to direct movement of the pin in somepredetermined manner, such as to direct the pin to move back from amaximum flow position to a position where the pin is in a range of pinpositions that control flow rate at a rate less than maximum flow orotherwise where the fluid is not at maximum pressure. The detection andsignaling of the piston's reaching the limit position is typically usedby the controller 10 and in the control algorithm in the same manner asdescribed in detail below.

FIG. 7 shows an alternative position sensing embodiment where aninductive position sensor 120 is mounted in a plate 122 that is mountedon the upper or rear surface of the housing 225 of actuator 226. Theinductive position sensor 120 senses the position of travel of thepiston 223 and its associated pin 200 by inductive sensing of theposition of a sensor target 110 mounted on the upper or rear end 223 aof piston 223. The position of travel or stroke distance 112 of thepiston 223 is thus detected by inductance sensing and a signal 114indicative of the position sensed can be sent to the master controller10 as shown in FIG. 7 and used in an algorithm as described herein forcontrolling movement of the pin 200 according to the algorithm.

As shown in the FIG. 1 embodiment, the master computer or controller 10receives signal inputs indicative of a fluid material condition frommaterial condition sensors 217 and indicative of position of the pinfrom sensors 100. The sensors 217 as shown in FIG. 1 sense a conditionof the fluid at a location or position that are downstream of thelocation at which that portion of the pins that control fluid flow rateare positioned. In the embodiment shown, the pins have bulbousprotrusions with outer surfaces 205 that control fluid flow rate byforming a gap with a complementary inner surface of the flow channel.The condition sensors sense a condition of the fluid at a location orposition that are downstream of the location at which fluid ratecontrolling surfaces 205 are positioned. As described below, in anembodiment where an extended pin, FIGS. 1, 4-6 is used to both controlflow rate and shut off flow at the gate with the distal end of the pin,the use of a position sensor 100 signal in combination with a conditionsensor signal to control flow rate during an injection cycle can work toprevent the controller 10 from instructing the actuator 226 to move thepin beyond a limit of forward/downstream travel that causes the distalend of the pin to prematurely close the gate and stop flow during thecourse of an injection cycle.

FIGS. 1, 4-6 show a system in which control of material flow is awayfrom the gate. The embodiment shown utilizes an extended valve pindesign in which the valve pin closes the gate after completion ofmaterial flow at the end of a cycle. The reverse taper pin controllablyvaries flow rate during a cycle by use of a reverse tapered controlsurface 205 for forming a gap 207 with a surface 209 of the manifold,FIGS. 4-6. The action of displacing the pin 200 in an upstream directionreduces the size of the gap 207, the maximum gap/flow position shown inFIG. 6, an intermediate gap/flow position shown in FIG. 5 and a stopflow/closed gap position shown in FIG. 4. Consequently, the rate ofmaterial flow through bores 208 and 214 of nozzle 215 and manifold 231,respectively, is reduced upon upstream movement from the FIG. 6 positionto the FIG. 4 position, thereby reducing the pressure measured by thepressure transducer 217.

The valve pin 200 reciprocates by movement of piston 223 disposed inactuator body 225. This actuator is described in U.S. Pat. No. 5,894,025the disclosure of which is incorporated herein by reference in itsentirety. The use of this embodiment of an actuator 226 enables easyaccess to valve pin 200 in that the actuator body 225 and piston 223 canbe removed from the manifold and valve pin simply by releasing retainingring 240.

Forward or downstream moving closure pins may also be used inconjunction with the position sensing flow control apparatus and methodof the present invention. Such forward or downstream movement pins aredescribed in detail in U.S. Pat. No. 6,361,300. In the forward closuremethod, the flow control gap between the bulbous protrusion of the pinand the manifold (or nozzle) bore surface decreases flow rate andpressure by forward movement with complete closure occurring uponmaximum forward movement as described in U.S. Pat. No. 6,361,300.Algorithms can be included in controller 10 for controlling pin (orram/cylinder used in conjunction with a shooting pot) position based onpin position sensing in the same manner as described herein for thereverse taper or upstream closure movement pin embodiments.

FIGS. 4-6 show the valve pin in three different positions. FIG. 4represents the position of the valve pin at the start of an injectioncycle. Generally, an injection cycle includes: 1) an injection periodduring which substantial pressure is applied to the melt stream from theinjection molding machine to inject the material in the mold cavity; 2)a reduction of the pressure from the injection molding machine in whichmelt material is packed into the mold cavity at a relatively constantpressure; and 3) a cooling period in which the pressure decreases tozero and the article in the mold solidifies. Just prior to the start ofinjection, tapered control surface 205 is in contact with manifoldsurface 209 to prevent any material flow. At the start of injection thepin 200 will be opened to allow material flow. To start the injectioncycle the valve pin 200 is displaced downstream toward the gate topermit material flow, as shown in FIG. 14. For applications where flowrates through different gates during a single injection cycle isdifferent, not all the pins will be opened initially, for some gates pinopening will be varied to sequence the fill into either a single cavityor multiple cavities at different time and different rates of flow. FIG.6 shows the valve pin at the end of the injection cycle after pack. Thepart is ejected from the mold while the pin is in the position shown inFIG. 15.

Pin position is controlled by a controller 10 based on position orpressure readings from one or both of sensors 100 or 217 that are fed tothe controller 10. In a preferred embodiment, the controller is aprogrammable controller, or “PLC,” for example, model number 90-30PLCmanufactured by GE-Fanuc. The controller compares the sensed position orpressure to a target position or pressure and adjusts the position ofthe valve pin via servo valve 212 to track the target position orpressure, displacing the pin forward toward the gate to increasematerial flow (and pressure) and withdrawing the pin away from the gateto decrease material flow (and pressure). In a preferred embodiment, thecontroller performs this comparison and controls pin position accordingto a PID algorithm.

The controller 10 performs these functions for all other injectionnozzles coupled to the manifold 231 during a single injection cycle.Associated with each gate is a valve pin, rotary valve, ram, cylinder orsome type of flow control mechanism to control the material flow rate.Also associated with each gate is either or both of a position sensorand material condition sensor, an input device for reading the outputsignal of the position and/or condition sensor, an algorithm for signalcomparison and PID calculation (e.g., the controller 10), a program,memory and human interface for setting, changing and storing a targetprofile (e.g., interface 214), an output circuit or program for sendinginstruction signals to a servomechanism that is interconnected to anddrives the actuator that is interconnected to and drives the pin, ram,rotary valve or the like that makes contact with the fluid flow, and anactuator to move/drive the valve pin, ram, cylinder, motor shaft or thelike. The actuator can be pneumatically, hydraulically or electricallydriven. The foregoing components associated with each gate to controlthe flow rate through each nozzle comprise a control zone or axis ofcontrol. Instead of a single controller used to control all controlzones, individual controllers can be used in a single control zone orgroup of control zones.

An operator interface 214, for example, a personal computer, is providedto store and input a particular target profile of position or pressureor both into controller 10. Although a personal computer is typicallyused, the interface 214 comprises any appropriate graphical or alphanumeric display, and can be mounted directly to the controller. As inprevious embodiments, the target position or pressure profile isselected for each gate associated therewith by pre-determining theprofile for each injection cycle (typically including at leastparameters for injection position or pressure, injection time, packposition or pressure and pack time), inputting the target profile intocontroller 10, and running the process. In the case of a multicavityapplication in which different parts are being produced in independentcavities associated with each nozzle (a “family tool” mold), it ispreferable to create each target profile separately, since differentlyshaped and sized cavities can have different profiles which produce theparts. For example, in a system having a manifold with four gates forinjecting into four separate cavities, to create a profile for aparticular gate, three of the four gates are shut off while the targetprofile is created for the fourth. Three of the four nozzles are shutoff by keeping the valve pins in the position shown in FIG. 4 or 6 inwhich no melt flow is permitted into the cavity.

To create a target profile for a particular gate, the injection moldingmachine is set at maximum injection pressure and screw speed, andparameters relating to the injection pressure or injection pin/ram/valveposition, injection time, pack pressure or pack pin/ram/valve position,and pack time are set on the controller 10 at values that the molderestimates will generate the best parts based on part size, shape,material being used, experience, etc. Multiple injection cycles arecarried out on a trial and error basis for each gate, with alterationsbeing made to the above parameters depending on the condition of thepart being produced during the trial cycle. When the most satisfactoryparts are produced, the profile that produced the most satisfactoryparts is determined for each gate and cavity associated therewith.Preferably, the target profiles determined for each gate are stored in adigital memory, e.g. on a file stored in interface 214 and used bycontroller 10 for production. The process can then be run under thecontrol of the controller 10 for all gates using the particularizedprofiles. The foregoing process of profile creation can be used with anynumber of gates. Although it is preferable to profile one gate andcavity at a time in a “family tool” mold application (while the othergates or their associated valves are closed), the target profiles canalso be created by running all nozzles simultaneously, and similarlyadjusting each gate profile according to the quality of the partsproduced. This would be preferable in an application where all the gatesare injecting into like cavities, since the profiles should be similar,if not the same, for each gate and cavity associated therewith.

In single cavity applications (where multiple nozzles from a manifoldare injecting into a single cavity), the target profiles would also becreated by running the nozzles at the same time and adjusting theprofiles for each nozzle according to the quality of the part beingproduced. The system can also be simplified without using interface 214,in which each target profile can be stored on a computer readable mediumin controller 10, or the parameters can be set manually on thecontroller.

The present invention can use any of the properties or states that aselected sensor is capable of sensing as a basis for creating a profileof target values for input as variables to an algorithm to be executedby controller 10. In particular, a target profile of the position of avalve pin, rotary valve or ram/cylinder may be used such componentsbeing directly responsible for controlling material flow. The values ofother injection machine, hotrunner or mold components or materials canalso be used to create a target profile that correlates to materialflow. For example, the position or condition of mechanical components ordrive materials associated with the direct flow control components canbe used where the condition or position of such associatedcomponents/materials accurately corresponds to the position of thedirect flow control components. For example, the pressure or temperatureof the hydraulic or pneumatic fluid that drive a servocontroller for anactuator can be used to create a target profile. Similarly, the degreeor state of electrical power/energy consumption or output of anelectrically powered motor that drives the movement of a pin, valve orram/cylinder can be used to create a target profile indicative ofposition of the direct flow controlling component.

In the FIGS. 1, 4-6 embodiments, position sensors 100 and conditionsensors 217 are shown as preferred for creating position and/or materialcondition target profiles as well as for recording and sending positionand/or material condition data to the controller 10 to be used in analgorithm that is designed to use such data as a basis for instructingmovement of the servomechanisms that control movement of the direct flowcontrol components such as valve pin 200.

For purposes of ease of description, FIGS. 9 a-d show sample targetprofiles based solely on pressure recorded by sensors 217. The X axisdata of the profiles/graphs shown in FIG. 9 a could alternatively beposition data that is generated by position sensors 100.

As shown in FIGS. 9 a-d, the graphs are material pressure versusinjection cycle time (235, 237, 239, 241) of the pressure sensed by fourpressure transducers associated with four nozzles mounted in manifoldblock 231, FIG. 1 (only two nozzles shown). The graphs of FIGS. 9 a-dare generated on the user interface 214 so that a user can observe thetracking of the actual pressure versus the target pressure during theinjection cycle in real time, or after the cycle is complete. The fourdifferent graphs of FIG. 9 a-d show four independent target pressureprofiles (“desired”) emulated by the four individual nozzles. Differenttarget profiles are desirable to uniformly fill different sizedindividual cavities associated with each nozzle, or to uniformly filldifferent sized sections of a single cavity.

The valve pin 200 associated with graph 235 is opened sequentially at0.5 seconds after the valves associated with the other three graphs(237, 239 and 241) were opened at 0.00 seconds. Referring back to FIGS.4-6, just before opening, the valve pins are in the position shown inFIG. 4, while at approximately 6.25 seconds at the end of the injectioncycle all four valve pins are in the position shown in FIG. 6. Duringinjection (for example, 0.00 to 1.0 seconds in FIG. 9 b) and pack (forexample, 1.0 to 6.25 seconds in FIG. 9 b) portions of the graphs, eachvalve pin is instructed to move to a plurality of positions bycontroller 10 to alter the pressure sensed by the pressure transducer217 associated therewith to track the target pressures of FIGS. 9 a-d.

Through the user interface 214, target profiles can be designed, andchanges can be made to any of the target profiles using standardwindows-based editing techniques. The profiles are then used bycontroller 10 to control the position of the valve pins 200. Forexample, FIG. 10 shows an example of a profile creation and editingscreen icon 300 generated on interface 214. Screen icon 300 is generatedby a windows-based application performed on interface 214.Alternatively, this icon could be generated on an interface associatedwith controller 10. Screen icon 300 provides a user with the ability tocreate a new target profile or edit an existing target profile for anygiven nozzle and cavity associated therewith. Screen icon 300 and theprofile creation text techniques described herein are described withreference to FIGS. 4-6, although they are applicable to all embodimentsdescribed herein.

In the pressure based profiles of FIGS. 9 a-d a profile 310 includes (x,y) data pairs, corresponding to time values 320 and pressure values 330which represent the desired pressure sensed by the pressure transducerfor the particular nozzle being profiled. The screen icon shown in FIG.10 is shown in a “basic” mode in which a limited group of parameters areentered to generate a profile. For example, in the foregoing embodiment,the “basic” mode permits a user to input start time displayed at 340,maximum fill pressure displayed at 350 (also known as injectionpressure), the start of pack time displayed at 360, the pack pressuredisplayed at 370, and the total cycle time displayed at 380. The screenalso allows the user to select the particular valve pin they arecontrolling displayed at 390, and name the part being molded displayedat 400. Each of these parameters can be adjusted independently usingstandard windows-based editing techniques such as using a cursor toactuate up/down arrows 410, or by simply typing in values on a keyboard.As these parameters are entered and modified, the profile will bedisplayed on a graph 420 according to the parameters selected at thattime.

By clicking on a pull-down menu arrow 391, the user can select differentnozzle valves in order to create, view or edit a profile for theselected nozzle valve and cavity associated therewith. Also, a part name400 can be entered and displayed for each selected nozzle valve. Thenewly edited profile can be saved in computer memory individually, orsaved as a group of profiles for a group of nozzles that inject into aparticular single or multi-cavity mold. The term “recipe” is used todescribe a group of profiles for a particular mold and the name of theparticular recipe is displayed at 430 on the screen icon.

To create a new profile or edit an existing profile, first the userselects a particular nozzle valve of the group of valves for theparticular recipe group being profiled. The valve selection is displayedat 390. The user inputs an alpha/numeric name to be associated with theprofile being created, for family tool molds this may be called a partname displayed at 400. The user then inputs a time displayed at 340 tospecify when injection starts. A delay can be with particular valve pinsto sequence the opening of the valve pins and the injection of meltmaterial into different gates of a mold. The user then inputs the fill(injection) pressure displayed at 350. In the basic mode, the ramp fromzero pressure to max fill pressure is a fixed time, for example, 0.3seconds. The user next inputs the start pack time to indicate when thepack phase of the injection cycle starts. The ramp from the fillingphase to the packing phase is also fixed time in the basic mode, forexample, 0.3 seconds.

The final parameter is the cycle time which is displayed at 380 in whichthe user specifies when the pack phase (and the injection cycle) ends.The ramp from the pack phase to zero pressure will be instantaneous whena valve pin is used to close the gate, as in the embodiment of FIG. 4due to the residual pressure in the cavity which will decay to zeropressure once the part solidifies in the mold cavity. User input buttons415 through 455 are used to save and load target profiles. Button 415permits the user to close the screen. When this button is clicked, thecurrent group of profiles will take effect for the recipe beingprofiled. Cancel button 425 is used to ignore current profile changesand revert back to the original profiles and close the screen. ReadTrace button 435 is used to load an existing and saved target profilefrom memory. The profiles can be stored in memory contained in theinterface 215 or the controller 10. Save trace button 440 is used tosave the current profile. Read group button 445 is used to load anexisting recipe group. Save group button 450 is used to save the currentgroup of target profiles for a group of nozzle valve pins. The processtuning button 455 allows the user to change the PID settings (forexample, the gains) for a particular nozzle valve in a control zone.Also displayed is a pressure range 465 for the injection moldingapplication.

Button 460 permits the user to toggle to an “advanced” mode profilecreation and editing screen. The advanced profile creation and editingscreen is shown in FIG. 11. The advanced mode allows a greater number ofprofile points to be inserted, edited, or deleted than the basic mode.As in the basic mode, as the profile is changed, the resulting profileis displayed. The advanced mode offers greater profitability because theuser can select values for individual time and pressure data pairs. Asshown in the graph 420, the profile 470 displayed is not limited to asingle pressure for fill and pack, respectively, as in the basic mode.In the advanced mode, individual (x, y) data pairs (time and pressure)can be selected anywhere during the injection cycle. To create and edita profile using advanced mode, the user can select a plurality of timesduring the injection cycle (for example 16 different times), and selecta pressure value for each selected time. Using standard windows-basedediting techniques (arrows 475) the user assigns consecutive pointsalong the profile (displayed at 478), particular time values displayedat 480 and particular pressure values displayed at 485. The next button490 is used to select the next point on the profile for editing. Prevbutton 495 is used to select the previous point on the profile forediting. Delete button 500 is used for deleting the currently selectedpoint. When the delete button is used the two adjacent points will beredrawn showing one straight line segment. The add button 510 is used toadd a new point after the currently selected point in which time andpressure values are entered for the new point. When the add button isused the two adjacent points will be redrawn showing two segmentsconnecting to the new point.

FIG. 8 shows an example of an algorithm executable by controller 10using both pressure and pin position as variables for control ofmovement of an extended pin 200 such as shown in FIGS. 4-6. Such analgorithm is useful particularly where material condition measurement bya sensor such as pressure sensor 217 is not alone sufficient toprecisely base control on. For example, as shown in FIG. 5, the pin isin a position where material flow is occurring during the injectionand/or pack stages of the injection cycle. As described above, when thetarget profile calls for an increase in pressure or a change in positionto increase material flow, the controller 10 will cause the valve pin200 to move forward to increase gap 207, which increases material flowand the pressure sensed by pressure transducer 217. However, if theinjection molding machine is not providing adequate pressure to meet thehigher pressure called for by the target pressure, moving the pin 200forward beyond the position shown in FIG. 5 will not increase thepressure sensed by transducer 217 enough to reach the target pressureand the controller 10 will continue to instruct the servomechanism 212to move the pin forward. This could lead to a loss of control sincemoving the pin further forward will tend to cause the distal end or head227 of the valve pin 200 to prematurely move to the position shown inFIG. 6 and close the gate 211.

The controller 10 may also not correctly instruct the servomechanism 212due to a time delay in the increase of pressure at the position ofsensor 217 and thus a delay in the accuracy of data being recorded bypressure sensor 217 relative to the assumed instantaneous pressureincrease on which the target profile of time versus pressure is based.Such discrepancy in sensor measurement can occur as a result of agradient in material pressure between bore 208, 213 and pressure in themachine barrel or channel 13, the delay in pressure increase resultingin the controller 10 instructing the pin 200 to move further downstreamthan desired, possibly to a point where the distal end 227 of the pin200 begins to restrict flow at the gate 211 or stops flow altogether.

Accordingly, to maintain precise control of the pin 200 according to thepredetermined pressure versus time profile, the controller is programmedwith an algorithm according to the flow chart of FIG. 8 where apredetermined limit position is selected, the limit position typicallybeing a position at which maximum flow or pressure occurs. In practice,the extended pin 200 embodiment has a plurality of maximum flow/pressurepositions extending over a length of travel somewhere between the closedposition shown in FIG. 6 and the position shown in FIG. 5. The limitposition is typically selected as being one or more of the maximumflow/pressure positions, however another position can be selected as thelimit position, if desired, for particular processing reasons peculiarto the part being produced.

As shown in FIG. 8, the algorithm executed by controller 10 includesinstructions that compare the signal being received from position sensor100 with the limit position to determine first whether the pin is at thelimit position at a time prior to the end of the injection and packphases of the cycle and, if so, the controller 10 then compares thepressure signal from sensor 217 to the profile pressure at the samepoint in time to determine whether an increase or decrease in pressureis called for by the profile. If the profile calls for a decrease inpressure at the point where the pin is at the limit position, controller10 reverts to control of the pin 200 according to the pressure profile,i.e. upstream movement to decrease pressure according to the pressureprofile. If the profile calls for an increase in pressure when the pinis at the limit position, the controller 10 sends instructions to theservomechanism 212 to either maintain the pin at its limit position orslightly decrease the pressure (i.e. move the pin upstream) until suchtime as the profile calls for a decrease in pressure along the course oftime of the cycle, i.e. along the length of the Y axis of FIGS. 9 a-d.Preferably, if the position sensor 100 signals that the pin 200 hastraveled beyond the limit position, the controller algorithm includesinstructions to direct the servomechanism to halt or reverse pin travelslightly.

As described above the position sensor 100 typically comprises avariable resistor or potentiometer that outputs a voltage signal thatvaries depending on the degree of extension of rod 102. Also asdescribed above, the sensor embodiment 130 of FIG. 4 a can be used todetect/sense travel of the pin 200 to or beyond the limit position andsignal the controller 10. Other sensors such as a linear voltagedifferential transformer (LVDT) 100 can be coupled to the pin shaft 200as shown in FIGS. 2, 3, to produce an output signal proportional to thedistance that pin 200 or piston 223 travels. Similarly, the inductiveposition sensor apparatus 112, 120 and its associated components, FIG. 7can be used to sense, record and signal pin or piston position to thecontroller 10. A sensor that operates via a variation in capacitance,i.e. a capacitative sensor, can be coupled to the piston 223 or pin 200.Where an electronic or electrically powered actuator is used to move thepin instead of the hydraulic or pneumatic actuators shown in FIGS. 1-7,the output signal to the electric motor or the servo-control to themotor can be used to estimate pin position, or an encoder mechanism canbe interconnected to the motor to generate an output signal proportionalto pin position.

At the end of the pack portion of the injection cycle, the valve pin 200is instructed by the algorithm to move all the way forward/downstream toclose off the gate as shown in FIG. 6. In the foregoing example, thefull stroke of the pin (from the position in FIG. 4 to the position inFIG. 6) is relatively small, e.g. 12 millimeters, and the rate of flowcontrol stroke length is a fraction of the total, e.g. 4 millimeters.The algorithm instructs the pin 200 to keep the gate 211 closed untiljust prior to the start of the next injection cycle when it is openedand pin 200 is moved to the position shown in FIG. 4. Immediately afterthe start of the next cycle, the pin 200 is instructed to move to thelimit position as shown in FIG. 8. While the gate 211 is closed, asshown in FIG. 6, the injection molding machine begins plastication forthe start of the next injection cycle as the part is cooled and ejectedfrom the mold.

FIGS. 12 and 13 show an alternative hot-runner system having flowcontrol in which the control of melt flow is still away from the gate asin previous embodiments. Use of the pressure transducer 1069 and PIDcontrol system is the same as in previous embodiments. In thisembodiment, however, the valve pin 1041 extends past the area of flowcontrol via extension 1110 to the gate. The valve pin is shown in solidlines in the fully open position and in phantom dashed lines in theclosed position. In addition to the flow control advantages away fromthe gate described above, the extended valve pin has the advantage ofshutting off flow at the gate with a tapered end 1112 of the valve pin1041.

Extending the valve pin to close the gate has several advantages. First,it shortens injection cycle time. In previous embodiments thermal gatingis used. In thermal gating, plastication does not begin until the partfrom the previous cycle is ejected from the cavity. This preventsmaterial from exiting the gate when the part is being ejected. Whenusing a valve pin, however, plastication can be performed simultaneouslywith the opening of the mold when the valve pin is closed, thusshortening cycle time by beginning plastication sooner. Using a valvepin can also result in a smoother gate surface on the part.

The flow control area is shown enlarged in FIG. 13. In solid lines thevalve pin is shown in the fully open position in which maximum melt flowis permitted. The valve pin includes a convex surface 1114 that tapersfrom edge 1128 of the stem 1102 of the valve pin 1041 to a throat area1116 of reduced diameter. From throat area 1116, the valve pin expandsin diameter in section 1118 to the extension 1110 which extends in auniform diameter to the tapered end of the valve pin.

In the flow control area the manifold includes a first section definedby a surface 1120 that tapers to a section of reduced diameter definedby surface 1122. From the section of reduced diameter the manifoldchannel then expands in diameter in a section defined by surface 1124 toan outlet of the manifold 1126 that communicates with the bore of thenozzle 1020. FIGS. 12 and 13 show the support ring style nozzle similarto FIGS. 1-3. However, other types of nozzles may be used such as, forexample, a threaded nozzle as shown in FIG. 8

As stated above, the valve pin is shown in the fully opened position insolid lines. In FIG. 13, flow control is achieved and melt flow reducedby moving the valve pin 1041 forward toward the gate thereby reducingthe width of the control gap 1098. Thus, surface 1114 approaches surface1120 of the manifold to reduce the width of the control gap and reducethe rate of melt flow through the manifold to the gate.

To prevent melt flow from the manifold bore 1019, and end the injectioncycle, the valve pin is moved forward so that edge 1128 of the valvepin, i.e., where the stem 1002 meets the beginning of curved surface1114, will move past point 1130 which is the beginning of surface 1122that defines the section of reduced diameter of the manifold bore 1019.When edge 1128 extends past point 1130 of the manifold bore melt flow isprevented since the surface of the valve stem 1002 seals with surface1122 of the manifold. The valve pin is shown in dashed lines where edge1128 is forward enough to form a seal with surface 1122. At thisposition, however, the valve pin is not yet closed at the gate. To closethe gate the valve pin moves further forward, with the surface of thestem 1002 moving further along, and continuing to seal with, surface1122 of the manifold until the end 1112 of the valve pin closes with thegate.

In this way, the valve pin does not need to be machined to close thegate and the flow bore 1009 of the manifold simultaneously, since stem1102 forms a seal with surface 122 before the gate is closed. Further,because the valve pin is closed after the seal is formed in themanifold, the valve pin closure will not create any unwanted pressurespikes. Likewise, when the valve pin is opened at the gate, the end 1112of the valve pin will not interfere with melt flow, since once the valvepin is retracted enough to permit melt flow through gap 1098, the valvepin end 1112 is a predetermined distance from the gate. The valve pincan, for example, travel 6 mm. from the fully open position to where aseal is first created between stem 1102 and surface 1122, and another 6mm. to close the gate. Thus, the valve pin would have 12 mm. of travel,6 mm. for flow control, and 6 mm. with the flow prevented to close thegate. Of course, the invention is not limited to this range of travelfor the valve pin, and other dimensions can be used.

FIGS. 14-18 show an alternative embodiment in which a load cell 1140 isused to sense the melt pressure acting on the face 1142 of valve pin1041. Where possible, reference characters are used that refer toelements common to FIG. 1. As in previous embodiments, an actuator 1049is used to translate the valve pin 1041 toward and away from the gate.The actuator 1049 includes a housing 1144 and a piston 1146 slidablymounted within the housing. The actuator is fed by pneumatic orhydraulic lines 1148 and 1150. Other actuators, for example, electricalactuators may also be used.

The valve pin 1041 is mounted to the piston 1146 so that valve pintranslates through the injection nozzle 1023 with movement of thepiston. The valve pin is mounted to the piston via a pin 1152. The pin1152 is slotted so that a clearance 1154 exists in which the valve pincan translate with respect to the pin 1152 and piston 1146. The valvepin bears against a button 1156 on the load cell 1140. The load cell1140 is mounted via screws 1158 to the piston. Thus, as shown in FIG.26, a force F₂ acting on the valve pin will cause the load button 1156to depress. Excitation voltages or other types of signals which indicatethe proportionate force on the load button 1156 are carried throughcable 1160 and fed to a controller 1151.

In operation, as seen in FIG. 14, the melt material is injected from aninjection molding machine nozzle 1011 into an extended inlet 1013mounted to a manifold 1015 through respective injection molding nozzles1021 and 1023 and into mold cavities 1162 and 1164. In the embodimentshown, a multi-cavity mold is shown in which nozzles 1021 and 1023inject melt material to form different size molded parts in cavities1162 and 1164, respectively. As stated above, a mold cavity withmultiple gates can be used, or multiple mold cavities with cavitieshaving the same size can be used.

When the valve pin 1041 is retracted to permit melt material to beinjected into the cavity 1162, the melt pressure will act on the face ofthe valve pin 1142 with the resulting force being transmitted throughthe shaft of the valve pin to the load sensor 1140 (see FIGS. 16-17).Thus, the load (F₂) sensed by load cell 1140 is directly related to themelt flow rate into the melt cavity.

Sheer stresses caused by the melt streaming downward over the valve pinwill tend to reduce the pressure sensed by the load cell but suchstresses are typically less than the nominal load due to the meltpressure. Thus, the resultant force F₂ will tend to compress the valvepin toward the load cell, with the possible exception of the initialopening of the valve, and the load cell provides an accurate indicatorof the melt pressure at the gate. If the application results in sheerstresses exceeding F₂, the load cell can be pre-loaded to compensate forsuch stresses.

Similar to previous embodiments described above, the signal transmittedthrough cable 1160 is compared by controller 1151 with a target value ofa target profile and the controller adjusts the position of the valvepin accordingly to increase or decrease flow rate. In this embodiment,the target profile is also a time versus pressure profile, but thepressure is the a result of the force of the pin on the load cell, asopposed to previous embodiments in which a pressure transducer directlysenses the force of the flow of the melt material. The profile iscreated in similar fashion to the embodiments described above: runningthe process and adjusting the profile until acceptable parts areproduced.

The valve pin controls the flow rate through the gate using a taperededge 1155 to form a control gap 1153 close to the gate. It should benoted, however, that any of the other valve pin designs described hereincan be used with the load cell 1140. Accordingly, when the pressuresensed by the load cell is less than the target pressure on the targetprofile, the controller 1151 signals the actuator to retract the valvepin to increase the size of the control gap 1153 and, consequently, theflow rate. If the pressure sensed by the load cell 1140 is greater thanthe target pressure, the controller 1151 signals the actuator todisplace the valve pin toward the gate to decrease the size of thecontrol gap 1153 and consequently, the flow rate.

The use of the load cell has an additional application shown in FIG.17A. In a single cavity multiple gate system it is often desirable toopen gates in a cascading fashion as soon as the flow front of the meltmaterial reaches the gate. When melt material 1166 has flowed into thegate area of the valve pin, a force F₂ from the melt in the cavity isexerted on the face 1142 of the valve pin.

In this way, gates can be sequentially opened in cascading fashion bysensing the force of the melt pressure on the face of the valve pin whenthe valve pin is closed. Given typical gate diameters of 0.2 inches andmelt pressures of 10,000 psi, the resulting force of 300 pounds isreadily measured by available load sensors, since the force of the cellequals the area of the gate times the pressure at the gate. Thus, thismelt detection can then be used to signal the opening of the gate as inthe sequential valve gate. This assures that the gate does not openprematurely.

FIGS. 18A and 18B show an alternative embodiment in which the sheerstress on the valve pin is reduced. The nozzle 1021 is designed toinclude a channel for melt flow 1168 and a bore 1170 through which thevalve pin reciprocates. As such, the flow does not cause any axial sheerstress on the valve pin and thus reduces errors in pressure sensing. Anindent 1172 is provided in the nozzle 1021 so that side load on thevalve pin is reduced, i.e., to equalize pressure on both sides of thevalve pin. An additional benefit to the configuration shown in FIGS. 18Aand 18B is that since the flow of material is away from the valve pin,the valve pin does not “split” the flow of material, which can tend tocause part lines or a flow streak on the molded part.

FIG. 19 shows another alternative embodiment of the present invention inwhich a ram 1565 is used to force material from well 1640 into cavity1525 at a controlled rate. The rate is controlled by signals sent fromcontroller 1535 to servo valve 1560A, which in turn controls thevelocity at which actuator 1560 moves ram 1565 forward.

In FIG. 19, actuator 1560 is shown in more detail including piston 1564,actuator chamber 1566, and hydraulic lines 1561 and 1562 controlled byservo valve 1560A. Energizing hydraulic line 1561 and filling chamber1566 causes piston 1564 and ram 1565 to move forward and displacematerial from well 1640 through channel 1585 and nozzle 1520, and intocavity 1525.

Accordingly, as in previous embodiments, a target profile is createdthat has been demonstrated to generate acceptable molded parts. In theembodiment of FIG. 19, however, the target profile represents targetvalues of the hydraulic pressure sensed by pressure transducer 1563, asopposed to directly sensing the material pressure. In operation, thecontroller compares the pressure signal sensed from pressure transducer1563 to the target pressure profile for gate 1555. If the pressuresensed is too low, the controller will increase the hydraulic pressurein line 1561 (which increases the velocity of the ram which increasesflow rate of the material), if the pressure is too high the controllerwill decrease the hydraulic pressure (which decreases the velocity ofthe ram which decreases the rate of material flow).

The target pressure profile of the hydraulic fluid will appear similarto a conventional material profile, since the pressure of the hydraulicfluid will rise rapidly during the injection portion of the cycle, leveloff during the pack portion of the cycle, and go to zero pressure ascycle ends the valve pin 1550 closes.

Although only one injection nozzle 1520 and cavity 1525 is shown, thereis a like arrangement associated with each injection nozzle of actuators1575, 1565, 1545, as well as solenoid valves 1540 and 1570 and servovalve 1560, to independently control the melt flowing from each gate,according to the target profile created for that gate. Also, although asingle cavity 1525 is shown, each nozzle may inject to multiple cavitiesor a single cavity mold. Only a single controller 1535, however, isneeded to control all the nozzles associated with manifold 1515.

Using the foregoing arrangement of FIG. 19, as in previous embodiments,the material flow from each nozzle of the manifold can be controlledindependently.

FIG. 20 shows another alternative embodiment of the present invention.The embodiment of FIG. 20 is substantially the same as the embodimentshown in FIG. 13 with the exception that pressure transducer 1217 hasbeen moved from manifold 1231 to inside the mold half 1650 which,together with mold half 1660, forms mold cavity 1670 in which the moldedpart is formed. Accordingly, in this embodiment, the target profilerepresents target values of the pressure sensed by pressure transducer1217 inside the cavity opposite the gate 1211.

The operation of the embodiment of FIG. 20 is the same as that describedin the embodiment shown in FIG. 5 in terms of target profile creationand use of valve pin 1200 to control the material flow (interface 1214is not shown but can be used). However, placing the pressure transducerin the cavity offers several advantages, for example, in the cavity thepressure transducer 1217 is not exposed to the high temperaturesgenerated by the manifold, as in FIG. 5. Also, the presence of thepressure transducer in the manifold may slightly disrupt material flowin the manifold. Another consideration in choosing whether to mount thetransducer in the mold or in the manifold is whether the mold geometrypermits the transducer to be mounted in the mold.

FIG. 21 is another alternative embodiment of the present invention thatis similar to FIG. 5. Target profile creation as well as the flowcontrol operation by valve pin 2000 is substantially the same asdescribed above. FIG. 21, however, does not include a pressuretransducer 217 as shown in FIG. 5 to directly sense the flow of meltmaterial into the cavity. Rather, similar to the embodiment shown inFIG. 19, the arrangement shown in FIG. 21 performs flow control bysensing the material pressure F₂ exerted by the melt material on thevalve pin.

In FIG. 14 measuring the load on the valve pin was performed using aload cell 1140, however, in FIG. 21, it is performed by pressuretransducers 1700 and 1710 mounted along hydraulic lines 1720 and 1730which lead to actuator chambers 1740 and 1750, respectively. Energizinglines 1720 and 1730 and filling actuator chambers 1740 and 1750, enablesaxial movement of piston 1223, thereby moving valve pin 1200 andaffecting the flow rate of the material into the cavity 1760 asdescribed above.

Pressure transducers 1700 and 1710 sense a differential pressure whichis directly related to the force exerted on valve pin 1200, which isdirectly related to the flow rate of the material. For example, when thematerial flow causes a force F₂ to act on valve pin 1200, the forcerelates up the valve pin to the piston, which in turn tends to increasethe pressure in chamber 1740 and line 1720 and decrease the pressure inchamber 1750 and line 1730, directly causing a change in the differencein the pressures sensed by the transducers 1700 and 1710. Accordingly,the differential pressure is directly related to the flow rate of thematerial into the cavity.

Once an acceptable target profile of differential pressure is developedusing techniques described above, the controller will cause the servovalve 1212 to track this target profile by altering the position of thevalve pin to change the flow rate of the material and track thedifferential pressure target profile. For example, if the differentialpressure is too high (e.g., the pressure sensed by transducer 1700 ishigher than the pressure sensed by transducer 1710 by an amount greaterthan the target differential pressure) the controller will cause servovalve to retract the valve pin to reduce the flow rate, thereby reducingthe force F₂ on the valve pin, thereby decreasing the pressure inchamber 1740 and line 1720, thereby decreasing the pressure sensed bytransducer 1700, thereby decreasing the difference in pressure sensed bytransducers 1700 and 1710. Note, in certain applications thedifferential pressure may be negative due to the sheer force of thematerial on the valve pin, this however will not affect the controller'sability to track the target profile.

As in the embodiment shown in FIG. 14, the embodiment shown in FIG. 21offers the advantage that it is not necessary to mount a pressuretransducer in the mold or the manifold. As in all previous embodiments,the embodiment shown in FIG. 21 enables the material flow from eachnozzle attached to the manifold to be independently profileable.

Having thus described certain embodiments of the present invention,various alterations, modifications, and improvements will readily occurto those skilled in the art. Such alterations, modifications, andimprovements are intended to be within the spirit and scope of theinvention. Accordingly, the foregoing description is by way of exampleonly, and not intended to be limiting. The invention is limited only asdefined in the following claims and the equivalents thereof.

1. In a molding machine having a manifold for distributing a meltmaterial flowing under pressure through a passage leading to a gate of amold cavity wherein the rate of flow of the melt material is determinedby positioning of a pin that is controllably movable through the channelto create a gap of controllable size between the pin and the passage,wherein the pin is disposed within the melt material on which the meltmaterial exerts a melt pressure force, an apparatus for controllingpositioning of the pin comprising: an actuator adapted to receive andcontrollably oppose the force exerted on the actuator by the meltmaterial through the pin and adjust the rate of material flow bypositioning of the pin and controlling the size of the gap, a controllercontrolling the actuator to oppose the melt pressure force receivedthrough the pin according to a predetermined profile of pressurecorresponding to the melt pressure force that is indicative of a desiredrate of material flow through the passage and into the cavity over thecourse of an injection cycle.
 2. In a molding machine having a manifoldfor distributing a melt material flowing under pressure through apassage leading to a gate of a mold cavity wherein the rate of flow ofthe melt material is determined by positioning of a pin that iscontrollably movable through the channel, wherein the pin has a flowcontrol surface that establishes a variable flow rate of the meltmaterial according to positioning of the pin within the passage, whereinthe pin is disposed within the melt material on which the melt materialexerts a melt pressure force, an apparatus for controlling positioningof the pin comprising: an actuator adapted to controllably move the pinthrough the passage and adjust positioning of the flow control surfaceof the pin within the passage, the actuator having a piston driven by adrive fluid that is adapted to receive the melt pressure force throughthe pin and to respond to the received force according to apredetermined profile of pressure of the drive fluid over the course ofan injection cycle, and, a controller controlling movement of the pistonaccording to the predetermined profile of pressure causing the piston toset the positioning of the flow control surface of the pin within thepassage at a series of predetermined positions within the passage overthe course of the injection cycle that correspond to the predeterminedprofile of pressure of the drive fluid over the course of the injectioncycle.
 3. In an injection molding system having a manifold to directmelt material through a passage to a gate which leads to a mold cavity,the passage having a valve pin movably disposed therein, the valve pinbeing controllably movable by an actuator and having a flow controlsurface that receives and exerts a melt pressure force on the actuator,the movement of the valve pin within the passage positioning the flowcontrol surface at varying positions within the passage that vary theflow rate of the melt material through the passage, the methodcomprising the steps of: (A) injecting material into the manifold; (B)predetermining a profile of pressure to be exerted by an actuator thatin opposition to the melt pressure force on the actuator receivedthrough the valve pin over the course of an injection cycle, thepredetermined profile of actuator pressure corresponding to apredetermined rate of flow of melt material over the course of theinjection cycle; (C) controlling the actuator to oppose the force of thematerial received through the valve pin according to the predeterminedprofile of actuator pressure over the course of the injection cycle. 4.The method of claim 3 wherein the actuator is adapted to receive theforce of the material exerted through the pin via an actuator drivefluid, the pressure of the drive fluid being controlled according to apredetermined profile of drive fluid pressure to oppose the force of thematerial.